Automatic adjustment device for brakes



Patented Apr. 11, `1939 @UNITED STATES y PATENT AUTOMATIC ADJUSTMENTDEVICE FOB BRAKES walter w. Riedel, Dayton, ohio, assigner to Generalporation` of Delaware Motors Corporation, Detroit, Mich., a cor-Application November 5, 1937, serial No. 172.8119

,ing\the releaseposition oi' brake shoes to aecom. l

l modatechanges in the lining thickness.

An'` object of the invention is to provide for such automaticallychanged positions of the shoes when in inactive position by aconstructionwhich pensive and which may be easily adjusted to `1i)effect any desired shoe clearance.

Referring to the drawing, numeral 5 is used to` designate a brake drum,such a drum as is usually carried by a vehicle wheel. The relativelynxedzbacking plate or drum closure is marked 1.

` Two opposed shoes marked 9 and il are to be 1 expanded into frictionalcontact with the drum.

'Ihese shoes are equipped with lining marked by v numeral i2. A coilspring Ilis shown as a yieldingmeans to withdraw the shoes from theiractive to Vtheirinactive positions. This spring is connected to bothshoes as shown. Secured to 30, the cover 1 in any convenient way is asubstantially conventional wheel cylinder I5. It is provided `withpistons I1 and lil and a spring 2| therebetween. Each piston 4isprovided with. a sealing cup 25. Between the pistons, hydraulic *35medium is injected from a suitable source, not

shown, through openingf. Provision is made for permitting the escape ofair by a suitable closure. not shown, associated with an opening 21.Push rods 29 serve v'as the means by which the movement of the pistonsis transmitted to the shoes.` Each push rod is formed with an end slot l3| adapted tostraddle the web of the shoe. 'Ihe opposite end of the pushrod is formed with fork's, reference'being made to Figure 2 where theseforks or arms are marked l33; The push rod has a sloping surface 35k atthe junction of theforks.

' A cap 31 carried bythe ends of the forks is seated in -a recess, ofthe piston. At each end o f the 5'0' cylinder there may' be used athreaded plug 4i and an dust guard.. Diametrically opposite aperturedbosses 45 and 41 are seen at each end of Y the cylinder. The lower bossis closed by a cap ll andv intol the upper boss there 'is adjustably.threaded a plug Ii.V The plug'll is equipped with (Cl. 188--79.5) Y

a rounded abutment 53 and the plug may be held in adjusted position by alock nut I5.

Reciprocable between the arms 33 and within 'the apertures of the bossesl5 and I1 is a plunger designated a's a whole by numeral 51. -The plung-5 er has cylindrical ends 59 and 6I which ends have a diameter which isless than that of the apershall be reliable, eiliclent and relativelyinex`- tures of the bosses. The upper end il has a I sloping surface63.' This slopingrsurface is in close proximity to but slightly'spacedlfrom the 10 abutment 53 on the end of the plug 5i when the plunger isin contact with the surfaces 65 and4 61' of the walls of the aperturesremotefrom the ends of the cylinder. Between the ends, the plunger has asloping surface 69 on one vside 15 thereof, this surface matching thesloping face 35 of the push rod. The opposite face 1| of thel plunger isstraight and is engaged by a hollow cup 13 within which is a lcoilspring 15, the spring seatedagainst the c'ap 31. The operation 20 of thedevice will be obvious but may be briefly desl'lbed. u l 1` Figure 1 isintended to represent the parts in the positions they occupy when theretractlng yielding spring Il has withdrawn the shoes from 25 contactwith the drum. The push rod in its movement of retrogression has carriedthe plunger along, with it. Thelimit of movement is determined by theengagement of the plunger with the cylinder at points Ii and 61. Thesloping face at is su'iilciently steep so that the yielding device I3 isunable to reciprocate the plunger` vertically. There isa gap betweenface 63 of the plunger and the knob S3. When fluid is admitted to thespace between the pistons they 35 spread apart and through theinstrumentality of the push rods the shoes are forced in to frictionalengagement withthe drum. As the push rod moves, the spring 15 causes theplunger to move alongfwith it. If the shoeflinings are not worn, drumcontact may be made before surface 63 of the plunger contacts the knob.53. Whenever the lining becomes worn :the knob 53 and the surface 63contact priorv to the full shoe and drum contact. When this occurs thecompletion of the movement of the push rod will be accompanied by avertical reciprocation of the plunger as a result of the shape ofsurface 63. This very vtical reciprocation determines. a. new positionof slope relative to slope 35. When the retract- 5o Iing spring again`returns the parts to their Vinl active position, and since in thisoperation there is no reciprocation of the plunger Ithe newly dentermined relative position of faces 35 and 68 reone wherein the liningclearance is substantially the same as before the lining became worn. Itwill be obvious that the return movement of the push rod is limited bythe engagement of the plunger with the surfaces 6.5 andv 61, whichengagement is accompanied by the opening up of f Vdent that the Vgapbetween the 4knob and surface 63 "is a measure of the shoe clearance andthat if it be desired tovary the shoe clearance, this objective isreadily accomplished by an vadjustment of the threaded plug. Theexpedient is simple and inexpensive.4 It is composed of but few and ruged parts. The gap may be readily adjusted t provide such clearanceastoaccommodate for all anticipated expansion and contraction of the drumwhich takes place as the result ofchanges in temperature so as to avoidany possibility of drag of the shoes.

It will also be readily appreciated that the invention is capable ofembodiment in a construction wherein such a push rod with its adjust#ment is actuated by means other than a reciprocable piston of ahydraulic cylinder. Furthermore it may be said that while the device hasbeen invented for use on.4 brakes it will be evident that it may be usedfor actuating other mechanical devices.

1. In combinatio a push rod, means to reciprocate said Vpus rod from aninactive to an active position, a plunger mounted to move bodilywithsaid push rod and also -across the path thereof, said push rod andplunger having cooperating sloping faces, spring means to hold saidfaces in contact, an abutment adapted to be engaged by said plunger when-moved jointly with the push rod to its inactive position, and

adjustable means to engage'and reciprocate said plunger along saidsloping faces to determine changed inactive'positions of the push rod.

2. In combination, a cylinder, a piston reciprocable therein, a push rodreciprocated by said piston, a plunger mounted in said cylinder forbodily movement jointly with the push rod and also for movement acrossthe path of movement of said push rod, said push rod and plunger hav-`ing sloping faces, spring means to hold said faces in contact saidcylinder constructed withan abutment wall to limit the return movementof the plunger and adjustable means to engage and reciprocate saidplunger along said sloping faces when the joint movement exceeds apredetermined'limit to determine changed idle positions of the push rodupon contact of the plunger with said abutment wall.

3. The invention" defined by` claim 2, 'said last named means comprisinga plug threaded into said cylinder and an end face formed on saidplunger and angularly related tothe axis thereof. 4. The inventiondefined by claim 2, together with yielding means to return said pushrod, said sloping face having an inclination such as to prevent relativevsliding of the plunger thereon under the influence of said yieldingmeans. v 5. In combination with a drum, a brake shoe adapted to engagesaid drum, a reciprocable brake actuating member, a push rod between andin contact with said shoe and actuating member, a

plunger mounted to move jointly with said pushv rod along the axis ofthe latter and also to move across the path of movement thereof, saidpush rod and plunger having sloping faces defining a plane at an angletothe paths of movement of both the plunger and push rod, spring meanscarried bythe push rod to hold said sloping faces in contact, meansadaptedl to engage and reciprocate said plunger when the joint movementof the p ush rod and plunger exceeds'a predetermined limit. l

6. `In combination with a drum, a brake shoe adapted to engage saiddrum, a reciprocable brake actuating member, a push rod between and incontact with said shoe and actuating member,

a plunger mounted to move jointly with said push rod along the axis ofthe latter and also to move across the path of movement thereof, saidpush rod and plunger having sloping, faces, spring means carried by thepush rod to hold said sloping faces in contact, said plunger having aninclined end faceand an adjustable member to engage said end face andreciprocate said plunger when the joint movement of the push rod andplunger exceeds a predetermined linut.

'7. The invention defined by claimv5, together with stop meanspositioned to be engaged by said plunger and limit its movement alongthe axis of the push rod.

8. InV combination, a brake drum, a brake shoe. a cylinder, a pistonmounted therein for reciprocation, a reciprocable push rod between andin contact with said piston and shoe.' said push rod having a slotterminating in a sloping face,'said. cylinder having diametricallyopposite apertures cylindrical insection, a plunger having a mid portionwith a sloping face engaging the sloping face of said push rod, springmeans within and carried by said push rod to maintain said sloping facesin contact, said plunger having cylindrical ends of less diameter than'.the diameter of said apertures and positioned therein, and means in on'eof said 9. The invention defined by claim 8, said last named meanscomprising a plug adjustable in said aperture and a sloping wall on theadjacent end of said plunger.

10. In combination, a brake" shoe, a hydraulic brake cylinder, a .pistonreciprocable therein, an axially reciprocable push rod between the shoeand the piston, said cylinder having diametrically opposite apertures, aplunger having cylindrical ends within but of less diameter than thediameter of said apertures, said push rod and plunger .having slopingfaces, spring means. carried by `said push rod to hold said faces incontact where-

